Graphical user interfaces (GUls) are well known. One key feature of all GUIs is a scrollable window to speed access to content. Typically, there is a graphical control on the edge of a window, called a scroll bar. Scrolling is accomplished by using a pointing device, such as a mouse, to move a cursor over the scroll bar.
FIG. 1 illustrates a typical prior art GUI display including a scrollable window. The display of a typically program may include menu bar 11, button bar 12, and data display 14. Vertical and horizontal scroll bars 15 (and graphical components of the scroll bars, such as arrow button 17 and scroll elevator 16) typically occupy one or two small portions of the screen. Therefore, it is difficult and/or time consuming for users to position a cursor exactly on the scroll bar and scroll bar components. Often, users overshoot the scroll bar and must use multiple motions to return the cursor to the proper location on the screen. Increasing the size of the scroll bar and its constituent components is not a desirable option since this would necessarily reduce the amount of display area available for data in the main data display portion 14.
To partially address the need for easier access to the GUI scrolling function, Gillick et al., in U.S. Pat. No. 5,530,455, describe a roller mouse that includes an extra wheel on its top surface. The extra wheel is used to scroll display windows without repositioning the cursor. However, utility of the Gillick et al. roller mouse is limited: it requires the addition of a complicated and expensive mechanical component to an existing mouse. Also, the roller mouse is not suitable for some desktop computers and most portable computers (that normally use trackballs, touchpads and similarly stationary pointing devices) because it requires space to accommodate a moving mouse.